-LRB- CNN -RRB- -- Sen. Mitch McConnell trounced his tea party-backed opponent in Kentucky 's Republican primary , leading a quartet of establishment GOP candidates to victories around the country Tuesday .

After an expensive and bitter campaign , the Senate minority leader led defeated challenger Matt Bevin 60 % -36 % , with 97 % of precincts reporting , according to numbers compiled by The Associated Press .

In addition to Kentucky , more moderate candidates won in Republican Senate primaries in Georgia and Oregon and in a House showdown in Idaho .

And the results in Kentucky , Georgia and Oregon could improve the GOP 's chances of taking back control of the Senate come November 's midterm elections .

Democrats hold a 55-45 voting majority in the Senate . They 're defending 21 of the 36 seats in play , half of them in Republican-leaning states or states where the two parties have similar levels of support .

The only states where the Democrats hope to play offense are Kentucky and Georgia .

If the GOP flips six Democratic held seats , they will win control of the Senate and McConnell will get a promotion from minority leader to majority leader .

`` We can take the reins of power away from Harry Reid and make this President accountable , '' McConnell said in his victory speech . `` Make me the majority leader , and Kentucky will lead America . ''

How McConnell crushed the tea party

Here are rundowns in the other state races :

Georgia : Republican businessman David Perdue will face Rep. Jack Kingston in a runoff in July . Perdue got 30 % of the vote ; Kingston received 27 % , according to numbers complied by The Associated Press . Perdue and Kingston beat out a trio of more conservative candidates in the GOP primary .

Among Democrats , Michelle Nunn easily won in her bid to follow in the footsteps of her father , longtime Sen. Sam Nunn .

Oregon : Sen. Jeff Merkley easily won the Democratic primary , and pediatric neurosurgeon Monica Wehby is the projected winner of the GOP Senate primary , topping a more conservative rival .

Idaho : Rep. Mike Simpson won the GOP primary in the state 's 2nd Congressional District , defeating tea party candidate Bryan Smith .

5 key primaries to watch Tuesday

Ugly and expensive race

Bevin , a businessman from Louisville , announced last summer he would challenge McConnell . He quickly gained the support of tea party activists and some influential Washington-based anti-establishment groups .

The race between the two men quickly turned ugly , and expensive , as both campaigns and outside groups spent big bucks .

The Senate Conservatives Fund dished out $ 1 million to support Bevin . But the group recently fell quiet with McConnell 's formidable lead in public opinion polls .

McConnell had a large campaign war chest , as well as backing from two Kentucky-based super PACs , and such powerful national groups as the U.S. Chamber of Commerce and the National Rifle Association .

Calls for unity

Soon after the race in Kentucky was called for McConnell , two of the groups backing Bevin -- the Senate Conservatives Fund and the Madison Project -- closed ranks behind the Senate minority leader .

`` Now it 's time for Republicans to unite for victory in November , '' said a statement from the Senate Conservatives Fund .

McConnell now faces a much tougher test against Kentucky Secretary of State Alison Lundergan Grimes .

Grimes , considered a rising Democratic star , faced no real opposition in her primary and already has had big names -- such as former President Bill Clinton -- team up with her on the campaign trail .

Grimes connected to big donors , big hitters

Speaking to supporters who held up signs that read `` Obama needs Alison Grimes '' and `` Kentucky needs Mitch McConnell , '' McConnell previewed his primary election theme : tying his opponent to President Obama , who lost Kentucky big in 2012 and is highly unpopular there now .

`` My opponent is in this race because Barack Obama and Harry Reid want her to be in this race , '' said McConnell , adding that `` a vote for my opponent is a vote for Obamacare and the President who sold it to us on a mountain of lies . ''

The pro-McConnell outside group Kentuckians for Strong Leadership said they would spend nearly $ 600,000 starting Wednesday to run a television commercial that ties Grimes to Obama .

Grimes , who spoke at her victory celebration just minutes after McConnell 's speech ended , fired back .

`` I 'm here to tell you tonight , my fellow Kentuckians , I am not an empty dress , I am not a rubber stamp and I am not a cheerleader . I am a strong Kentucky woman who is an independent thinker who , when I 'm Kentucky 's next senator , the decisions I make will be what 's best for the people of the Commonwealth of Kentucky , not partisan interests , '' Grimes declared .

She 's expected to use McConnell 's GOP leader status and his frequent moves to block legislation to make him the symbol of gridlock in Washington .

The most recent polling indicates the two candidates are all tied up .

When all 's said and done , the race could become the most expensive Senate campaign in history , breaking the $ 82 million record set in the 2012 Senate battle in Massachusetts .

Key races to watch

CNN 's Steve Brusk , Dana Davidsen and Holly Yan contributed to this report .

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David Perdue and Jack Kingston will have a runoff in Georgia 's GOP Senate primary

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In Oregon , Sen. Jeff Merkley , Dr. Monica Wehby win Democratic , GOP Senate primaries

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Six states held primary elections Tuesday

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Republican Sen. Mitch McConnell faces Democrat Alison Lundergan Grimes